A party crasher pretending to be Matt Damon‘s publicist caused havoc at Gwen Stefani‘s show for her fashion line, L.A.M.B., at Lincoln Center — forcing organizers to hold front-row seats for Damon, who was in LA, and sending paparazzi into a frenzy.

A man who called himself Jay Berman contacted reps at several fashion houses and agencies during Fashion Week posing as a rep for the “Bourne” star and Victoria’s Secret models Chanel Iman, Alessandra Ambrosio, Coco Rocha and Lily Aldridge.

On Thursday, Berman called the Schiff Company, which reps Stefani, and claimed to be Damon’s point person in New York while he promoted his new movie, “The Adjustment Bureau.” He requested three tickets for Damon, his wife, Luciana Barroso, and a friend named Peter Gianquinto. The tickets were arranged with organizers at Paul Wilmot Communications. Photographers and reporters swarmed the front row expecting the A-list star and his wife, anxiously waiting for them to take up two reserved seats. But they never showed up, and instead two burly security men took the seats.

Confusion continued through last evening, when Wilmot organizers still believed Barroso attended the show with Gianquinto, but sat in the fourth row because they didn’t want to be photographed.

However, Damon’s rep, Jennifer Allen, confirmed to us that Damon and Barroso had been in LA since Tuesday morning, since Damon is shooting a movie there. “He’s never been to a fashion show, to my knowledge,” said Allen, who has repped Damon for 16 years. “No one called me to check.”

Allen also said Berman’s name has come up in the past. “I did get a call six months ago from ESPN about the same thing. Same guy, same name saying he was trying to set Matt up for some ESPN event.”

Other Fashion Week publicists said they had also been contacted by Berman — who used an e-mail address from PMKHBHPR, clearly nothing to do with p.r. powerhouse PMK — trying to get into shows and parties for G-Star and Catherine Malandrino, but he was rejected. Berman hung up on us when we called to ask about his con act.